Solutions­Day 4­9.notebook
March 05, 2014
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Solutions­Day 4­9.notebook
March 05, 2014
Other ways to measure concentration:
Molarity (M) = the number of moles of solute per liter of solution:
1M = 1 mol solute 1 Liter solution
(1 Molar solution)
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Solutions­Day 4­9.notebook
March 05, 2014
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Solutions­Day 4­9.notebook
March 05, 2014
1. What is the molarity of a solution that contains 0.25 mol of NaCl in 100 ml solution?
M = # mol = 0.25 mol
0.1L
vol
= 2.5M
2. How many g of NaCl would be dissolved in 500 mL H2O to create a 1M sol'n?
M = x mol ; x = 0.5 mol NaCl
0.5 L
0.5 mol x 58.5 g NaCl = 29.3 g NaCl
1 mol NaCl
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Solutions­Day 4­9.notebook
March 05, 2014
3. What is the molarity of a solution that contains 67 g AlCl3 dissolved in a 2.0 L solution? ?M = x mol
2.0 L
GFM: 133.5 g AlCl3/mol AlCl3
67 g AlCl3 x 1 mol AlCl3 = 0.50 mol
133.5 g AlCl3 0.50 mol = 0.25M
2.0 L
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Solutions­Day 4­9.notebook
March 05, 2014
Molality (m) =
# of moles solute dissolved in one Kg of solvent
1m = 1 mole 1 Kg solvent
1. What is the molality of a solution that contains 2.5 g NH3 in 175 g H2O?
GFM of NH3 = 17 g/mol
2.5 g NH3 x 1 mol NH3 = 0.15 mol NH3
17 g NH3
m = 0.15 mol NH3 = 0.8 m (molals)
0.175 Kg H2O
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Solutions­Day 4­9.notebook
March 05, 2014
2. How many g AgNO3 are needed to prepare a 0.125 m sol'n in 250 mL H2O?
0.125m = 0.125 mol AgNO3 x 0.250Kg H2O
1Kg H2O
0.125m = 0.125 mol AgNO3 x 250g H2O
1000g H2O
= 0.03 mol AgNO3
(GFM AgNO3 = 170 g AgNO3/mol AgNO3)
0.03 mol AgNO3 x 170 g AgNO3 =
1 mol AgNO3
5.1 g AgNO3
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